Optical cables are extensively used in military aircraft as interconnects in aircraft frames. Avionic interconnect applications, and Unmanned Aircraft applications, will benefit from development of a more rugged, durable, bend and kink insensitive, lighter weight optical cable fiber.
Optical cables are also used extensively in the operation of underwater vehicles, referred to as Remotely Operated Vehicles (ROVs). These vehicles are connected to the surface ship via a composite tether cable that consists of electrical cables for power and control and optical cables for data and real time video imagery. The optical cables are usually much thinner than the electrical cables and typically reside in the interstices between the electrical cables. It is critical that the optical cables be both high strength and flexible. The flexibility makes them survive the compressive forces that result from the surrounding massive electrical power, particularly during fabrication and also when the composite tether is wound around a mandrel. This is another application that would benefit from a high strength, non-kinking, low cost optical cable.
Another application is the use of optical tethers to maintain two way communication between a mother ship and a ROV deployed in the deep seas. As the ROV maneuvers in the water or on the ocean floor it may retrace its path so that the connected tether loops on itself. As the loop becomes tighter the cable will kink and the optical fiber may break or optical transmission will be impeded. (This is similar to a garden hose which is being pulled at one end and forms a loop somewhere along its length. Often the loop will become progressively tighter and form a kink and water will no longer flow through the garden hose). This phenomenon is called hockling.
It is desirable to have a non-hockling optical cable such that as a loop in the cable becomes smaller, it flips open forming a 360° twist instead of a kink. The twist has no effect on optical transmission while the kink is disastrous. Therefore it is desirable to have an optical cable that is high strength, non-kinking and non-hockling.
Thin, high tensile strength, low cost optical cables have been formed by extruding liquid crystal polymer (LCP) layers over standard commercially available optical fibers (U.S. Pat. No. 7,570,853). LCPs are thermoplastic polymers that have high tensile strength, high chemical resistance and excellent moisture barrier properties. However, LCPs are not very flexible so cables utilizing LCP are also not very flexible and thus prone to kinking when deployed in the field.
Consequently, it is a principal object of the present invention to provide optical cables of low-cost, high strength, and resistant to kinking and hockling.
It is another object of the present invention to provide optical cables incorporating LCP layers to enhance tensile strength and provide protection against moisture.
Other objects of the invention will be obvious and will, in part, appear hereinafter when the following detailed description is read in connection with the appended drawings.